Fig. 1

The life cycle of Physcomitrella patens. Development in Physcomitrella patens starts from the haploid spore, which forms protonema, a tip growing filamentous tissue. During the juvenile-to-adult transition of the moss gametophyte, the protonema forms buds which contain a three-faced apical meristematic cell (Harrison et al. 2009) able to generate the leafy gametophore. Within several weeks of inducing conditions (15 °C short day), male and female sexual organs develop on the apex of the gametophores. Male gametangia (antheridia) release flagellate gametes that need a water film to travel to the female gametangia (archaegonia). From the diploid (2n) zygote, a sporophyte is formed on top of the gametophyte, which in turn forms spores (1n) by meiosis. Ripe sporophytes open by rupture and release spores which germinate to generate protonema. Scale bars: a 6 μm, b 50 μm, c 1 mm, d 500 μm, e 200 μm, f 100 μm